1. Field of the Invention
This invention relates to a swing data measuring device in which various data of swing really played when a baseball player exercises bat swing, such as level of passing trace of a bat, angle of the trace with respect to a prescribed reference line and the speed of the bat passing through the trace, can be detected optically and displayed as digital value being understandable readily. Swing data obtained may be utilized as scientific index to improve swing of the player himself.
2. Description of the Prior Art
Measurement of swing data of a bat swung by a baseball player can be performed by optically detecting that two lines being nearly perpendicular to the ground are intersected by the bat and processing the intersection and the time required for the intersecting by electronic means.
A swing data measuring device on the basis of this principle in the prior art is shown in FIG. 1, and use state thereof is in FIG. 2. In FIG. 2, reference numeral 1 designates a baseball bat to be swung by a player, numeral 2 a light reflecting sheet applied to a peripheral surface of the bat 1 adjacent to top end preferably to peripheral surface of sweet spot portion, and numeral 3 a swing data measuring device. The device 3 as shown in FIG. 1 comprises four light emitting/receiving apparatuses 31, 32, 33, 34, a display unit 4, and switch buttons S.sub.1, S.sub.2 for changing the display content in the display unit 4. The light emitting/receiving apparatuses 31-34 comprise light emitting means A.sub.1, A.sub.2, A.sub.3, A.sub.4 for emitting light beams 3a, 3b, 3c, 3d intersecting the swing plane S of the bat 1 shown in FIG. 2, and light receiving means C.sub.1, C.sub.2, C.sub.3, C.sub.4 for receiving light reflected from the light reflecting sheet 2 applied to the bat 1.
Principle of the swing data measurement in this measuring device will be described referring to FIG. 3. In FIG. 3, X-axis is on the measuring apparatus 3 and Y-axis is taken on middle portion of distance between light beams from 3a to 3d. The trajectory axis S intersects the light beams 3a-3d and Y-axis at points P.sub.1 -P.sub.5. P.sub.o is the intersection between beams 3a, 3b or between beams 3c, 3d, and the distance h.sub.o between P.sub.o and X-axis is constant value preset at the beam system. The distance h between the origin 0 of X-Y coordinates and the point P.sub.5 represents level of the swing plane, and .theta..sub.1 represents inclination angle of the trajectory axis S with respect to the horizontal plane. If the swing speed v is constant within the line segment P.sub.1 P.sub.4, the level h of the swing plane, the inclination angle .theta..sub.1 and the speed v are represented respectively as follows: ##EQU1## T.sub.1, T.sub.3 represent the traveling time of line segments P.sub.1 P.sub.2 and P.sub.2 P.sub.4 respectively and may be measured by the measuring device 3.
FIG. 4 shows constitution of a measuring unit 35 which is provided with four pairs of light emitting sections A and light receiving sections C. In the light emitting section A, modulation signal from a modulator 6 passes through a driver 7 and is emitted as optical signal from a light emitting element 8. The optical signal is focused into luminous flux with prescribed spread by means of a lens system 9 and projected upwards through a beam splitter 10 as a half-mirror.
Reflected light from the light reflecting sheet 2 of the bat 1 intersecting the luminous flux is reflected about 90.degree. by means of the beam splitter 10 and focused by the lens system 11 and entered into the light receiving element 12. Light-receiving signal is outputted from the light receiving element 12 and noise component is removed from the light-receiving signal by the filter amplifier 13 and the detector 14 thereby analog waveform corresponding to the reflected light is produced. The analog waveform is converted into digital waveform by a digitizer 15 and then outputted. The output is processed by a processing unit (not shown) and the processing result is displayed as level, angle of the swing plane and the swing speed in a display unit.
The swing data measuring device in the prior art as above described can measure the level of the swing plane, the angle thereof and the speed of the bat on the swing plane and display them. However, for the player using the measuring apparatus to know above-mentioned data scarcely becomes index to improve technique of the player. Because discrimination is impossible regarding to what degree above-mentioned data is different from data obtained by the correct or best swing.